1. Field of the Invention
The invention relates to a process for decaffeinating green coffee, optionally pre-moistured with water or steam, by treatment with organic solvents and removal of the solvent residues by steaming.
2. Description of the Prior Art
In decaffeinating green coffee, a solvent is required which extracts caffeine with high selectivity, i.e. which does not extract also other coffee ingredients. Moreover, the solvent employed must be removable completely from the treated coffee.
Most known processes for decaffeinating green coffee employ halogen-containing hydrocarbons such as trichloroethylene, dichloroethane or chloroform on account of the selective dissolving capability of these solvents for caffeine. The use of the solvents, however, recently has given rise to objections under the aspect of health.
In other known processes esters, ketones, light hydrocarbons or ethers have been employed. However, esters are readily saponified, and it is difficult to sufficiently remove saponification products, i.e. acids and alcohols, from the coffee. Due to their relatively high polarity ketones have insufficient selectivity for removal of caffeine. Hydrocarbons and ethers dissolve caffeine only sparingly so that relatively high temperatures and long treating periods must be employed when these solvents are used.